Temporal coherence among tropical coastal lagoons: a search for patterns and mechanisms

A Caliman,Pm Lopes,Fa Esteves,Fd Azevedo,Rd Guariento,Apf Pires,Al Suhett,Jm Santangelo,V Scofield,Lb Quesado,Lf Sanches,Vf Farjalla,Cc Marinho,Rl Bozelli,Es Fonte,Ls Carneiro

doi:10.1590/s1519-69842010000400011

Abstract

Temporal coherence (i.e., the degree of synchronicity of a given variable among ecological units within a predefined space) has been shown for several limnological features among temperate lakes, allowing predictions about the structure and function of ecosystems. However, there is little evidence of temporal coherence among tropical aquatic systems, where the climatic variability among seasons is less pronounced. Here, we used data from long-term monitoring of physical, chemical and biological variables to test the degree of temporal coherence among 18 tropical coastal lagoons. The water temperature and chlorophyll-a concentration had the highest and lowest temporal coherence among the lagoons, respectively, whereas the salinity and water colour had intermediate temporal coherence. The regional climactic factors were the main factors responsible for the coherence patterns in the water temperature and water colour, whereas the landscape position and morphometric characteristics explained much of the variation of the salinity and water colour among the lagoons. These results indicate that both local (lagoon morphometry) and regional (precipitation, air temperature) factors regulate the physical and chemical conditions of coastal lagoons by adjusting the terrestrial and marine subsidies at a landscape-scale. On the other hand, the chlorophyll-a concentration appears to be primarily regulated by specific local conditions resulting in a weak temporal coherence among the ecosystems. We concluded that temporal coherence in tropical ecosystems is possible, at least for some environmental features, and should be evaluated for other tropical ecosystems. Our results also reinforce that aquatic ecosystems should be studied more broadly to accomplish a full understanding of their structure and function.

Highlights

The properties of aquatic ecosystems have recently been considered in the context of landscapes, where lakes in a geographic area are examined to identify common and long-term behaviour patterns for one or more variables (Carpenter et al, 2007; Das et al, 2009; Magnuson et al, 1990; Soranno et al, 1999)
The coastal lagoons sampled here provide an ideal range of conditions to test the hypotheses of temporal coherence
All of the lagoons were exposed to the same climate, soil type and surrounding vegetation, but differed significantly in the morphometry, landscape position and trophic status

Summary

Introduction

The properties of aquatic ecosystems have recently been considered in the context of landscapes, where lakes in a geographic area are examined to identify common and long-term behaviour patterns for one or more variables (Carpenter et al, 2007; Das et al, 2009; Magnuson et al, 1990; Soranno et al, 1999). It is defined as the degree to which the temporal series of environmental features (biotic and/ or abiotic) obtained in a subset of aquatic environments within a predefined space are positively correlated (i.e., vary synchronously) Extrinsic forces, such as climate or episodic disturbances operating over broad spatial scales, can promote synchronous behaviour in a suite of system variables (Blenckner et al, 2007; Das et al, 2009), while internal forces, such as differences in the lake size and morphometry, and species composition and food-source, often lead to a more idiosyncratic temporal behaviour, indicating the predominance of local-scale regulators (Webster et al, 2000; Kent et al, 2007; Weyhenmeyer 2008; Lansac-Toha et al, 2008; Takahashi et al, 2008)

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Conclusion